Method of enhancing an antitumor T cell response by administering an anti-IL-6 receptor antibody

ABSTRACT

An objective of the present invention is to provide novel therapeutic agents for cancer, which have an excellent antitumor effect in cancer patients by enhancing their immune function. The present inventors discovered that the administration of at IL-6 inhibitor and/or gemcitabine or a salt thereof to tumor-bearing organisms yields an excellent antitumor T cell response-enhancing effect, and completed the present invention. In addition, the present inventors discovered that the T cell response-enhancing effect produces an excellent antitumor effect.

TECHNICAL FIELD

The present invention relates to compositions for enhancing the antitumor T cell response. More specifically, the present invention relates to compositions for enhancing the antitumor T cell response, which contain an interleukin 6 (IL-6) inhibitor and/or gemcitabine or a salt thereof, or compositions for enhancing the antitumor T cell response which contain an IL-6 inhibitor, characterized in that an IL-6 inhibitor is administered in combination with gemcitabine or a salt thereof.

BACKGROUND ART

IL-6 is a cytokine also called B-cell stimulating factor 2 (BSF2) or interferon β2. IL-6 was discovered as a differentiation factor involved in the activation of B-cell lymphocytes (Non-Patent Document 1), and was later revealed, to be a multifunctional cytokine that influences the function of various cells (Non-Patent Document 2). It has been reported to induce maturation of T lymphocyte cells (Non-Patent Document 3).

IL-6 transmits its biological activity via two kinds of proteins on the cell. The first is the IL-6 receptor, which is a ligand-binding protein to which IL-6 binds, with a molecular weight of about 80 kDa (Non-Patent Documents 4 and 5). The IL-6 receptor is present in a membrane-bound form that penetrates the cell membrane. It is expressed on the cell membrane, and also as a soluble IL-6 receptor, which mainly consists of the extracellular region of the membrane-bound form.

Patent Document 1 describes various forms of anti-IL-6R (IL-6 receptor) antibodies, for example, humanized anti-IL-6R antibodies and chimeric anti-IL-6R antibodies. Patent Document 2 describes therapeutic agents for chronic rheumatoid arthritis and synovial cell growth inhibitors, which contain as an active ingredient an IL-6 antagonist such as an anti-IL-6R antibody. Patent Document 3 describes the treatment of diseases caused by IL-6 production, such as plasmacytosis, hyperimmunoglobulinemia, anemia, nephritis, cachexia, rheumatism, Castleman's disease, and mesangial proliferative nephritis. Patent Document 4 describes preventive and/or therapeutic agents, containing an anti-IL-6R antibody as an active ingredient, for sensitized T cell-mediated diseases, for example, multiple sclerosis, uveitis, chronic thyroiditis, delayed hypersensitivity, contact dermatitis, and atopic dermatitis.

Patent Document 5 describes therapeutic agents for systemic lupus erythematosus, which contain an anti-IL-6R antibody as an active ingredient. Patent Document 6 describes therapeutic agents for Crohn's disease, which contain an anti-IL-6R antibody as an active ingredient. Patent Document 7 describes therapeutic agents for pancreatitis, which contain an anti-IL-6R antibody as an active ingredient. Patent Document 8 describes therapeutic agents for psoriasis, which contain an anti-IL-6R antibody as an active ingredient. Furthermore, Patent Document 9 describes therapeutic agents for juvenile chronic arthritis, which contain, an anti-IL-6R antibody as an active ingredient. Patent Document 10 describes agents for suppressing neural invasion of a cell, which contain an anti-IL-6R antibody as an active ingredient, and teaches that they can inhibit human pancreatic cancer neuroinvasion.

Gemcitabine (hydrochloride) (Gemzar (Registered Trademark)) is a cytosine analog which inhibits DNA synthesis by inhibiting ribonucleotide reductase and competing with dCTP for incorporation into DNA, and is currently used as a therapeutic agent against some types of cancers such as pancreatic cancer. Gemcitabine is also used as a concomitant agent in radiotherapy; however, no significant improvement in the long-term survival of pancreatic cancer patients has been achieved. Furthermore, there have been some attempts using other effective combination therapies; however, no reports so far indicate the improvement of survival rate.

Prior art documents related to the present invention include:

-   Non-Patent Document 1: Hirano, T. et al., Nature (1986) 324, 73-76 -   Non-Patent Document 2: Akira, S. et al., Adv. in Immunology (1993)     54, 1-78 -   Non-Patent Document 3: Lotz, M. et al., J. Exp. Med. (1988) 167,     1253-1258 -   Non-Patent Document 4: Taga, T. et al., J. Exp. Med. (1987) 166,     967-981 -   Non-Patent Document 5: Yamasaki, K. et al., Science (1987) 241,     825-828 -   Patent Document 1: WO92/19759 -   Patent Document 2: WO96/11020 -   Patent Document 3: WO96/12503 -   Patent Document 4: WO98/42377 -   Patent Document 5: WO98/42377 -   Patent Document 6: WO99/47170 -   Patent Document 7: WO00/10607 -   Patent Document 8: WO02/3492 -   Patent Document 9: WO02/080969 -   Patent Document 10: WO2009/148148

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

An objective of the present invention is to provide novel cancer therapeutic agents that produce an excellent antitumor effect by enhancing the immune function of cancer patients.

Means for Solving the Problems

The present inventors conducted dedicated studies to achieve the objective described above. As a result, the present inventors revealed that the administration of an IL-6 inhibitor and/or gemcitabine or a salt thereof ameliorates the immunosuppression caused by aberrant proliferation of immature myeloid cells (ImC), and results in an enhanced T cell response in tumor-bearing organisms. Thus, the present inventors completed the present invention. In addition, the present invention demonstrates that the combined use of an IL-6 inhibitor and gemcitabine or a salt thereof synergistically enhances the T cell response and produces an excellent antitumor effect.

Specifically, the present invention provides the following [1] to [17];

[1] A composition for enhancing an antitumor T cell response in a tumor-bearing organism, which comprises an interleukin 6 (IL-6) inhibitor and/or gemcitabine or a salt thereof.

[2] The composition of [1] for enhancing the antitumor T cell response, wherein the IL-6 inhibitor and gemcitabine or salt thereof is administered concomitantly.

[3] The composition of [1] or [2], wherein the IL-6 inhibitor is a substance that binds to an IL-6 receptor.

[4] The composition of [3], wherein the substance that binds to an IL-6 receptor is an anti-IL-6 receptor antibody.

[5] The composition of [4], wherein the anti-IL-6 receptor antibody is a chimeric, humanized, or human antibody.

[6] The composition of any one of [1] to [5], wherein the gemcitabine or salt thereof is gemcitabine hydrochloride.

[7] A method for enhancing an antitumor T cell response, which comprises the step of administering an IL-6 inhibitor and/or gemcitabine or a salt thereof to a tumor-bearing organism.

[8] The method of [7], wherein the IL-6 inhibitor is a substance that binds to an IL-6 receptor.

[9] The method of [8], wherein the substance that binds to an IL-6 receptor is an anti-IL-6 receptor antibody.

[10] The method of [9], wherein the anti-IL-6 receptor antibody is a chimeric, humanized, or human antibody.

[11] The method of any one of [7] to [10], wherein the gemcitabine or salt thereof is gemcitabine hydrochloride.

[12] An IL-6 inhibitor which is used for enhancing an antitumor T cell response in a tumor-bearing organism.

[13] The inhibitor of [12], wherein the IL-6 inhibitor and gemcitabine or salt thereof are used concomitantly to enhance the antitumor T cell response.

[14] The inhibitor of [13], wherein the IL-6 inhibitor is a substance that binds to an IL-6 receptor.

[15] The inhibitor of [4], wherein the substance that binds to an IL-6 receptor is an anti-IL-6 receptor antibody.

[16] The inhibitor of [15], wherein the anti-IL-6 receptor antibody is a chimeric, humanized, or human antibody.

[17] The inhibitor of any one of [13] to [16], wherein the gemcitabine or salt thereof is gemcitabine hydrochloride.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the result of assessing the antitumor effect of GEM (Gemzar: gemcitabine hydrochloride) administration to BALB/c mice inoculated with a cell line of methylcholanthrene-induced squamous cancer CMC-1.

FIG. 2 is a graph showing the result of flow cytometric analysis for the absolute number of cells of each population in the spleen after administration of GEM (Gemzar: gemcitabine hydrochloride) to CMC-1-inoculated tumor-bearing mice.

FIG. 3 is a graph showing the result of assessing the growth ability of CD8⁺ cells after stimulation with an anti-CD3 antibody where the CD8⁺ cells were obtained from the spleen after administration of cyclophosphamide, 5-FU, or GEM to CMC-1-inoculated tumor-bearing mice.

FIG. 4 is a graph showing the result of measuring tumor diameter after administration of GEM to CMC-1-innoculated tumor-bearing mice.

FIG. 5 is a graph showing the result of flow cytometric assessment for the percentage of OVA-specific CD8⁺ cytotoxic T cells in LLC-OVA-inoculated C57BL6 mice after GEM administration, where LLC-OVA was prepared by introducing the ovalbumin (OVA) gene into mouse lung cancer cell line LLC.

FIG. 6 is a graph showing the result of measuring the serum IL-6 level in BALB/c mice inoculated with cell line of methylcholanthrene-induced fibrosarcoma CMC-G4.

FIG. 7 is a graph showing the result of determining the IFN-γ level by ELISA alter stimulation of spleen cells with anti-CD3 antibody or concanavalin A (ConA) following administration of an anti-IL-6R antibody to CMC-G4-inoculated tumor-bearing mice.

FIG. 8 is a graph showing the result of measuring tumor diameter after administration of an anti-IL-6R antibody to CMC-G4-inoculated tumor-bearing mice.

FIG. 9 is a graph showing the result of measuring tumor diameter after administration of GEM and anti-IL-6R antibody in combination to CMC-G4-inoculated tumor-bearing mice.

MODE FOR CARRYING OUT THE INVENTION

Herein, “IL-6 inhibitor” refers to a substance that blocks IL-6 signaling and inhibits the biological activity of IL-6. Specifically, the IL-6 inhibitors include, for example, substances that bind to IL-6, substances that bind to an IL-6 receptor, and substances that bind to gp130. The IL-6 inhibitors also include substances that inhibit phosphorylation of STAT3 which is important for the intracellular signaling of IL-6, such as AG490. The IL-6 inhibitors include, but are not particularly limited to, anti-IL-6 antibodies, anti-IL-6 receptor antibodies, anti-gp130 antibodies, IL-6 variants, soluble IL-6 receptor variants, partial peptides of IL-6, partial peptides of an IL-6 receptor, and low-molecular-weight compounds having an activity equivalent thereto.

In a preferred embodiment, the IL-6 inhibitors include IL-6 receptor inhibitors, in particular, anti-IL-6 receptor antibodies.

The origin of antibodies used in the present invention is not particular by limited; however, the antibodies are preferably derived from mammals, and more preferably from humans.

An antibody of the present invention can be prepared as a polyclonal or monoclonal antibody using known methods. In particular, monoclonal antibodies derived from mammals are preferably used in the present invention. Monoclonal antibodies derived from mammals include those produced by hybridomas and those produced by hosts transformed with an expression vector carrying an antibody gene using genetic engineering techniques. Typically, these antibodies block transmission of the biological activity of IL-6 into cells by binding to IL-6, an IL-6 receptor, gp130, or the like.

Basically, monoclonal antibody-producing hybridomas can be prepared using known techniques as follows. Specifically, immunization is carried out by a conventional immunization method using as a sensitizing antigen an IL-6 receptor, IL-6, gp130, or such. The resulting immune cells are fused with known parental cells by a conventional cell fusion method. Then, monoclonal antibody-producing cells are screened using a conventional screening method.

Specifically, monoclonal antibodies can be produced as follows. For example, when anti-IL-6 receptor antibodies are prepared, a human IL-6 receptor or mouse IL-6 receptor for use as a sensitizing antigen for obtaining antibodies can be obtained by using the IL-6 receptor genes and/or amino acid sequences disclosed in European Patent Application Publication No. EP 325474 and Japanese Patent Application Kokai Publication No. (JP-A) Hei 3-155795, respectively.

There are two kinds of IL-6 receptor proteins: one expressed on the cell membrane and the other separated from the cell membrane (soluble IL-6 receptors) (Yasukawa, K. et al., J. Biochem. (1990) 108, 673-676). The soluble IL-6 receptor essentially consists of the extracellular region of the cell membrane-bound IL-6 receptor, and differs from the membrane-bound IL-6 receptor in that it lacks the transmembrane region or both the transmembrane and intracellular regions. Any IL-6 receptor may be employed as an IL-6 receptor protein, so long as it can be used as a sensitizing antigen for producing an anti-IL-6 receptor antibody used in the present invention.

After transforming an appropriate host cell with a known expression vector system inserted with an IL-6 receptor gene sequence, the desired IL-6 receptor protein is purified from the inside of the host cell or from the culture supernatant using a known method. This purified IL-6 receptor protein may be used as a sensitizing antigen. Alternatively, a cell expressing the IL-6 receptor or a fusion protein of the IL-6 receptor protein and another protein may be used as a sensitizing antigen.

Likewise, when IL-6 is used as a sensitizing antigen for preparation of antibodies, human IL-6 can be obtained by using the gene and/or amino acid sequences of IL-6 disclosed in Eur. J. Biochem (1987) 168, 543-550, J. Immunol. (1988) 140, 1534-1541, or Agr. Biol. Chem. (1990) 54, 2685-2688. Alternatively, for a sensitizing antigen for preparation of anti-gp130 antibodies, the gene and/or amino acid sequences of gp130 disclosed in European Patent Application Publication No. EP 411946 can be used.

Mammals to be immunized with a sensitizing antigen are not particularly limited, but are preferably selected considering compatibility with the parent cell used for cell fusion. Generally, rodents such as mice, rats, and hamsters are used.

Animals are immunized with sensitizing antigens according to known methods. For example, as a general method, animals are immunized by intraperitoneal or subcutaneous injection of a sensitizing antigen. Specifically, the sensitizing antigen is preferably diluted or suspended in an appropriate amount of phosphate-buffered saline (PBS), physiological saline or such, mixed with an appropriate amount of a general adjuvant (e.g., Freund's complete adjuvant), emulsified, and then administered to a mammal several times, every four to 21 days. In addition, an appropriate carrier may be used for immunization with a sensitizing antigen.

Following such immunization, an increased level of a desired antibody in serum is confirmed and then immune cells are obtained from the mammal for cell fusion. Preferred immune cells for cell fusion include, in particular, spleen cells.

The mammalian myeloma cells used as parent cells, i.e. as partner cells to be fused with the above immune cells, include various known cell strains, for example, P3X63Ag8.653 (Kearney, J. F. et al., J. Immunol (1979) 123, 1548-1550), P3X63Ag8U.1 (Current Topics in Microbiology and Immunology (1978) 81, 1-7), NS-1 (Kohler, G. and Milstein, C., Eur. J. Immunol. (1976) 6, 511-519), MPC-11 (Margulies, D. H. et al., Cell (1976) 8, 405-415), SP2/0 (Shulman, M. et al., Nature (1978) 276, 269-270), F0 (de St. Groth, S. F. et al., J. Immunol. Methods (1980) 35, 1-21), S194 (Trowbridge, I. S., J. Exp. Med. (1978) 148, 313-323), R210 (Galfre, G. et al., Nature (1979) 277, 131-133), and such.

Basically, cell fusion of the aforementioned, immune cells and myeloma cells can be performed using known, methods, for example, the method of Milstein et al. (Kohler, G. and Milstein, C., Methods Enzymol. (1981) 73, 3-46), and such.

More specifically, the aforementioned cell fusion is achieved in general nutrient culture medium in the presence of a cell fusion enhancing agent. For example, polyethylene glycol (PEG), Sendai virus (HVJ), and such are used as fusion enhancing agents. Further, to enhance fusion efficiency, auxiliary agents such as dimethyl sulfoxide may be added depending on the need.

The ratio of immune cells to myeloma cells used is preferably, for example, 1 to 10 immune cells for each myeloma cell. The culture medium used for the aforementioned cell fusion is, for example, the RPMI 1640 or MEM culture medium, which are suitable for proliferation of the aforementioned myeloma cells. A general culture medium used for culturing this type of cell can also be used. Furthermore, serum supplements such as fetal calf serum (FCS) can be used in combination.

For cell fusion, the fusion cells (hybridomas) of interest are formed by mixing predetermined amounts of an aforementioned immune cell and myeloma cell in an aforementioned culture medium, and then adding and mixing a concentration of 30% to 60% (w/v) PEG solution (e.g., a PEG solution with a mean molecular weight of about 1,000 to 6,000) pre-heated to about 37° C. Then, cell fusion agents and such that are unsuitable for the growth of hybridomas can be removed by repeatedly adding an appropriate culture medium and then removing the supernatant by centrifugation.

The above hybridomas are selected by culturing cells in a general selection culture medium, for example, HAT culture medium (a culture medium containing hypoxanthine, aminopterin, and thymidine). Culture in HAT culture medium is continued for a sufficient period, generally several days to several weeks, to kill cells other than the hybridomas of interest (unfused cells). Then, a standard limited dilution method is performed to screen and clone hybridomas that produce an antibody of interest.

In addition to the methods for immunizing non-human animals with antigens for obtaining the aforementioned hybridomas, desired human antibodies with the activity of binding to a desired antigen or antigen-expressing cell can be obtained by sensitizing a human lymphocyte with a desired antigen protein or antigen-expressing cell in vitro, and fusing the sensitized B lymphocyte with a human myeloma cell (e.g., U266) (see, Japanese Patent Application Kokoku Publication No. (JP-B) Hei 1-59878 (examined, approved Japanese patent application published for opposition)). Further, a desired human antibody can be obtained by administering an antigen or antigen-expressing cell to a transgenic animal that has a repertoire of human antibody genes, and then following the aforementioned method (see, International Patent Application Publication Nos. WO 93/12227, WO 92/03918, WO 94/02602, WO 94/25585, WO 96/34096, and WO 96/33735).

The thus-prepared hybridomas which produce monoclonal antibodies can be subcultured in a conventional culture medium and stored in liquid nitrogen for a long period.

When obtaining monoclonal antibodies from the aforementioned hybridomas, the following methods may be employed: (1) methods where the hybridomas are cultured according to conventional methods and the antibodies are obtained as a culture supernatant; (2) methods where the hybridomas are proliferated by administering them to a compatible mammal and the antibodies are obtained as ascites; and so on. The former method is preferred for obtaining antibodies with high purity, and the latter is preferred for large-scale antibody production.

For example, anti-IL-6 receptor antibody-producing hybridomas can be prepared by the method disclosed in JP-A (Kokai) Hei 3-139293. Such hybridomas can be prepared by injecting a PM-1 antibody-producing hybridoma into the abdominal cavity of a BALB/c mouse, obtaining ascites, and then purifying a PM-1 antibody from the ascites; or by culturing the hybridoma in an appropriate medium (e.g., RPMI 1640 medium containing 10% fetal bovine serum, and 5% BM-Condimed H1 (Boehringer Mannheim); hybridoma SFM medium (GIBCO-BRL); PFHM-II medium (GIBCO-BRL), etc.) and then obtaining PM-1 antibody from the culture supernatant.

Recombinant antibodies can be used as the monoclonal antibodies of the present invention, wherein the antibodies are produced using genetic recombination techniques by cloning an antibody gene from a hybridoma, inserting the gene into an appropriate vector, and then introducing the vector into a host (see, for example, Borrebaeck, C. A. K. and Larrick, J. W., Therapeutic Monoclonal Antibodies, published in the United Kingdom by Macmillan Publishers Ltd, 1990).

More specifically, mRNAs coding for antibody variable (V) regions are isolated from cells that produce antibodies of interest, such as hybridomas. mRNAs can be isolated by preparing total RNAs according to known methods, such as the guanidine ultracentrifugation method (Chirgwin, J. M. et al., Biochemistry (1979) 18, 5294-5299) and the AGPC method (Chomczynski, P. et al., Anal. Biochem, (1987) 162, 156-159), and preparing mRNAs using an mRNA Purification Kit (Pharmacia) and such. Alternatively, mRNAs can be directly prepared using a QuickPrep mRNA Purification Kit (Pharmacia).

cDNAs of the antibody V regions are synthesized from the obtained mRNAs using reverse transcriptase. cDNAs may be synthesized using an AMV Reverse Transcriptase First-strand cDNA Synthesis Kit and so on. Further, to synthesize and amplify the cDNAs, the 5′-RACE method (Frohman, M. A. et al., Proc. Natl. Acad. Sci. USA (1988) 85, 8998-9002; Belyavsky, A. et al., Nucleic Acids Res. (1989) 17, 2919-2932) using 5′-Ampli FINDER RACE Kit (Clontech) and PCR may be employed. A DNA fragment of interest is purified from the obtained PCR products and then ligated with a vector DNA. Then, a recombinant vector is prepared using the above DNA and introduced into Escherichia coli or such, and then its colonies are selected to prepare a desired recombinant vector. The nucleotide sequence of the DNA of interest is confirmed by, for example, the dideoxy method.

When a DNA encoding the V region of an antibody of interest, is obtained, the DNA is ligated with a DNA that encodes a desired antibody constant region (C region), and inserted into an expression vector. Alternatively, a DNA encoding an antibody V region may be inserted into an expression vector comprising a DNA of an antibody C region.

To produce an antibody to be used in the present invention, as described below, an antibody gene is inserted into an expression vector such that it is expressed under the control of an expression regulating region, for example, air enhancer and promoter. Then, the antibody can be expressed by transforming a host cell with this expression vector.

In the present invention, to reduce heteroantigenicity against humans and such, artificially modified genetic recombinant antibodies, for example, chimeric antibodies, humanized antibodies, or such, can be used. These modified antibodies can be prepared using known methods.

A chimeric antibody can be obtained by ligating a DNA encoding an antibody V region, obtained as above, with a DNA encoding a human antibody C region, then inserting the DNA into an expression vector and introducing it into a host for production (see, European Patent Application Publication No. EP 125023; International Patent Application Publication No. WO 92/19759). This known method can be used to obtain chimeric antibodies useful for the present invention.

Humanized antibodies are also referred to as reshaped human antibodies, and are antibodies wherein the complementarity determining regions (CDRs) of an antibody from a mammal other than human (e.g., a mouse antibody) are transferred into the CDRs of human antibodies. General methods for this gene recombination are also known (see, European Patent Application Publication No. EP 125023, International Patent Application Publication No. WO 92/19759).

More specifically, DNA sequences designed such that the CDRs of a mouse antibody are ligated with the framework regions (FRs) of a human antibody are synthesized by PCR from several oligonucleotides produced to contain overlapping portions at their termini. The obtained DNA is ligated with a human antibody C region-encoding DNA and then inserted into an expression vector. The expression vector is introduced into a host to produce the humanized antibody (see, European Patent Application Publication No. EP 239400, International Patent Application Publication No. WO 92/19759).

The human antibody FRs to be ligated via the CDRs are selected so that the CDRs form suitable antigen binding sites. The amino acid(s) within the FRs of the antibody variable regions may be substituted as necessary so that the CDRs of the reshaped human antibody form an appropriate antigen binding site (Sato, K. et al., Cancer Res. (1993) 53, 851-856).

Human antibody heavy chain C regions are generally used for the chimeric and humanized antibodies, and include Cγ etc. For example, Cγ1, Cγ2, Cγ3, or Cγ4 may be used. Human antibody light chain C regions include, for example, Cκ and Cλ. Furthermore, to improve the stability of the antibodies or their production, the human, antibody C regions may be modified.

Chimeric antibodies consist of the variable region of an antibody derived from a non-human mammal and the constant region of an antibody derived from a human; humanized antibodies consist of the CDRs of an antibody derived from a non-human mammal and the framework regions and constant regions derived from a human antibody. They have reduced antigenicity in the human body, and are thus useful as antibodies for use as pharmaceuticals.

Preferred specific examples of humanized antibodies for use in the present invention include the humanized PM-1 antibody (see, International Patent Application Publication No. WO 92/19759).

Furthermore, in addition to the aforementioned methods for obtaining human antibodies, techniques for obtaining human antibodies by panning using a human antibody library are also known. For example, the variable regions of human antibodies can be expressed on phage surfaces as single chain antibodies (scFv) by using the phage display method, and antigen-binding phages can then be selected. By analyzing the genes of the selected phages, DNA sequences coding for the human antibody variable regions that bind to the antigen can be determined. Once the DNA sequence of an scFv that binds to the antigen is revealed, an appropriate expression vector comprising the sequence can be constructed to obtain a human antibody. These methods are already known, and the publications of WO 92/01047, WO 92/20791, WO93/06213, WO 93/11236, WO 93/19172, WO 95/01438, and WO 95/15388 can be used as reference.

The antibody genes constructed above can be expressed according to conventional methods. When a mammalian cell is used, the antibody gene can be expressed, using a DNA in which the antibody gene to be expressed is functionally ligated to a useful commonly used promoter and a poly A signal downstream of the antibody gene, or a vector comprising the DNA. Examples of a promoter/enhancer include the human cytomegalovirus immediate early promoter/enhancer.

Furthermore, other promoters/enhancers that can be used, for expressing the antibodies for use in the present invention include viral promoters/enhancers from retroviruses, polyoma viruses, adenoviruses, simian virus 40 (SV40), and such; and also include mammalian cell-derived promoters/enhancers such as human elongation factor 1α (HEF1α).

For example, when the SV40 promoter/enhancer is used, the expression can be easily performed by following the method by Mulligan et al. (Mulligan, R. C. et al., Nature (1979) 277, 108-114). Alternatively, in the case of the HEF1α promoter/enhancer, the method by Mizushima et al. (Mizushima, S. and Nagata S., Nucleic Acids Res. (1990) 18, 5322) can be easily used.

Production systems using prokaryotic cells include those using bacterial cells. Known bacterial cells include E. coli and Bacillus subtilis.

When E. coli is used, an antibody gene can be expressed by functionally ligating a conventional promoter, a signal sequence for antibody secretion, and the antibody gene to be expressed. Examples of the promoter include a lacZ promoter, araB promoter and such. When a lacZ promoter is used, genes can be expressed according to the method of Ward et al. (Ward, E. S. et al., Nature (1989) 341, 544-546; Ward, E. S. et al., FASEB J. (1992) 6, 2422-2427); and the araB promoter may be used according to the method of Better et al. (Better, M. et al., Science (1988) 240, 1041-1043).

When the antibody is produced into the periplasm of E. coli, the pel B signal sequence (Lei, S. P. et al., J. Bacteriol. (1987) 169, 4379-4383) may be used as a signal sequence for antibody secretion. The antibodies produced into the periplasm are isolated, and then used after appropriately refolding the antibody structure (see, for example, WO 96/30394).

As the replication origin, those derived from SV40, polyoma virus, adenovirus, bovine papilloma virus (BPV) and such may be used. In addition, to enhance the gene copy number in a host cell system, the expression vector may comprise the aminoglycoside phosphotransferase (APH) gene, thymidine kinase (TK) gene, E. coli xanthine-guanine phosphoribosyltransferase (Ecogpt) gene, dihydrofolate reductase (dhfr) gene, or such as a selection marker.

Any production system may be used to prepare the antibodies for use in the present invention. The production systems for antibody preparation include in vitro and in vivo production systems. In vitro production systems include those using eukaryotic cells or prokaryotic cells.

When eukaryotic cells are used as hosts, the production systems include those using animal cells, plant cells, or fungal cells. Such animal cells include (1) Mammalian cells, for example, CHO, COS, myeloma, baby hamster kidney (BHK), HeLa, Vero, and such; (2) amphibian cells, for example, Xenopus oocyte, and (3) insect cells, for example, sf9, sf21, Tn5, and such. Known plant cells include cells derived from Nicotiana tabacum, which may be cultured as a callus. Known fungal cells include yeasts such as Saccharomyces (e.g., S. cerevisiae), mold fungi such as Aspergillus (e.g., A. niger), and such.

Antibodies can be obtained by using transformation to introduce an antibody gene of interest into these cells, and then culturing the transformed cells in vitro. Cultures are conducted according to known methods. For example, DMEM, MEM, RPMI 1640, IMDM may be used as the culture medium, and serum supplements such as FCS may be used in combination. Further, cells introduced with antibody genes may be transferred into the abdominal cavity or such of an animal to produce the antibodies in vivo.

On the other hand, in vivo production systems include those using animals or plants. Production systems using animals include those that use mammals or insects.

Mammals that can be used include goats, pigs, sheep, mice, bovines and such (Vicki Glaser, SPECTRUM Biotechnology Applications, 1993). Further, insects that can be used include silkworms. When using plants, tobacco may be used, for example.

An antibody gene is introduced into these animals or plants, the antibody is produced in the body of the animals or plants, and this antibody is then recovered. For example, an antibody gene can be prepared as a fusion gene by inserting it into the middle of a gene encoding a protein such as goat β casein, which is uniquely produced into milk. DNA fragments comprising the fusion gene, which includes the antibody gene, are injected into goat embryos, and the embryos are introduced into female goats. The desired antibody is obtained from milk produced by the transgenic animals born to the goats that received the embryos, or produced from progenies of these animals. The transgenic goats can be given hormones to increase the volume of milk containing the desired antibody that they produce (Ebert, K. M. et al., Bio/Technology (1994) 12, 699-702).

When silkworms are used, the silkworms are infected with a baculovirus inserted with a desired antibody gene, and the desired antibody is obtained from the body fluids of these silkworms (Maeda, S. et al., Nature (1985) 315, 592-594). Moreover, when tobacco is used, the desired antibody gene is inserted into a plant expression vector (e.g., pMON530) and the vector is introduced into bacteria such as Agrobacterium tumefaciens. This bacterium is used to infect tobacco (e.g., Nicotiana tabacum) such that desired antibodies can be obtained from the leaves of this tobacco (Julian, K.-C. Ma et al. Eur. J. Immunol. (1994) 24, 131-138).

When producing antibodies using in vitro on in vivo production systems, as described above, DNAs encoding an antibody heavy chain (H chain) and light chain (L chain) may be inserted into separate expression vectors and a host is then co-transformed with the vectors. Alternatively, the DNAs may be inserted into a single expression vector for transforming a host (see International Patent Application Publication No. WO 94/11523).

The antibodies used in the present invention may be antibody fragments or modified products thereof, so long as they can be suitably used in the present invention. For example, antibody fragments include Fab, F(ab′)2, Fv, and single chain Fv (scFv), in which the Fvs of the H and L chains are linked via an appropriate linker.

Specifically, the antibody fragments are produced by treating antibodies with enzymes, for example, papain or pepsin, or alternatively, genes encoding these fragments are constructed, introduced into expression vectors, and these are expressed in appropriate host cells (see, for example, Co, M. S. et al., J. Immunol. (1994) 152, 2968-2976; Better, M. & Horwitz, A. H., Methods in Enzymology (1989) 178, 476-496; Plueckthun, A. & Skerra, A., Methods in Enzymology (1989) 178, 497-515; Lamoyi, E., Methods in Enzymology (1989) 121, 652-663; Rousseaux, J. et al., Methods in Enzymology (1989) 121, 663-666; Bird, R. E. et al., TIBTECH (1991) 9, 132-137).

An scFv can be obtained by linking the H-chain V region and the L-chain V region of an antibody. In the scFv, the H-chain V region and the L-chain V region are linked via a linker, preferably via a peptide linker (Huston, J. S, et al., Proc. Natl. Acad. Sci USA (1988) 85, 5879-5883). The V regions of the H and L chains in an scFv may be derived from any of the antibodies described above. Peptide linkers for linking the V regions include, for example, arbitrary single chain peptides consisting of 12 to 19 amino acid residues.

An scFv-encoding DNA can be obtained, by using a DNA encoding an H chain or a V region and a DNA encoding an L chain or a V region of the aforementioned antibodies as templates, using PCR to amplify a DNA portion that encodes the desired amino acid sequence in the template sequence and uses primers that define the termini of the portion, and then further amplifying the amplified DNA portion with a DNA that encodes a peptide linker portion and primer pairs that link both ends of the linker to the H chain and L chain.

Once an scFv-encoding DNA has been obtained, an expression vector comprising the DNA and a host transformed with the vector can be obtained according to conventional methods. In addition, scFv can be obtained according to conventional methods using the host.

As above, these antibody fragments can be produced from the host by obtaining and expressing their genes. Herein, an “antibody” encompasses such antibody fragments.

Antibodies bound to various molecules, such as polyethylene glycol (PEG), may also be used as modified antibodies. Herein, an “antibody” encompasses such modified antibodies. These modified antibodies can be obtained by chemically modifying the obtained antibodies. Such methods are already established in the art.

Antibodies produced and expressed as above can be isolated from the inside or outside of the cells or from the hosts, and then purified to homogeneity. The antibodies for use in the present invention can be isolated and/or purified using affinity chromatography. Columns to be used for the affinity chromatography include, for example, protein A columns and protein G columns. Carriers used for the protein A columns include, for example, HyperD, POROS, Sepharose FF and such. In addition to the above, other methods used for the isolation and/or purification of common proteins may be used, and are not limited in any way.

For example, the antibodies used for the present invention may be isolated and/or purified by appropriately selecting and combining chromatographies in addition to affinity chromatography, filters, ultrafiltration, salting-out, dialysis, and such. Chromatographies include, for example, ion-exchange chromatography, hydrophobic chromatography, gel filtration, and such. These chromatographies can be applied to high performance liquid chromatography (HPLC). Alternatively, reverse phase HPLC may be used.

The concentration of the antibodies obtained as above can be determined by absorbance measurement, ELISA, or such. Specifically, absorbance is determined by appropriately diluting the antibody solution with PBS(−), measuring absorbance at 280 nm, and calculating the concentration (1.35 OD=1 mg/ml). Alternatively, when using ELISA, the measurement can be performed as follows: Specifically, 100 μl of goat anti-human IgG (TAG) diluted to 1 μg/ml with 0.1 M bicarbonate buffer (pH 9.6) is added to a 96-well plate (Nunc) and incubated overnight, at 4° C. to immobilize the antibody. After blocking, 100 μl of an appropriately diluted antibody of the present invention or an appropriately diluted sample comprising the antibody, and human IgG (CAPPEL) are added as a standard, and incubated for one hour at room temperature.

After washing, 100 μl of 5,000× diluted alkaline phosphatase-labeled anti-human IgG (BIO SOURCE) is added and incubated for one hour at room temperature. After another wash, substrate solution is added and incubated, and the absorbance at 405 nm is measured using a Microplate Reader Model 3550 (Bio-Rad) to calculate the concentration of the antibody of interest.

Specifically, examples of anti-IL-6 antibodies include, but are not particularly limited to, the antibodies MH166 (Matsuda, T. et al, Eur. J. Immunol (1998) 18, 951-956) and SK2 (Sato K et al. The abstracts of the 21st Annual Meeting of the Japanese Society for Immunology (1991) 21, 166).

Specifically, examples of anti-IL-6 receptor antibodies include, but are not particularly limited to, the antibodies MR16-1 (Tamura, T. et al., Proc. Natl. Acad. Sci, USA (1993) 90, 11924-11928), PM-1 (Hirata, Y. et al., J. Immunol (1989) 143, 2900-2906), AUK 12-20, AUK64-7, and AUK 146-15 (International Patent Application No. WO 92-19759). Of these, the PM-1 antibody is an example of preferred monoclonal antibodies against the human IL-6 receptor, while the MR16-1 antibody is an example of preferred monoclonal antibodies against the mouse IL-6 receptor; however, the antibodies are not limited thereto. Examples of preferred humanized anti-IL-6 receptor antibodies include a humanized PM-1 antibody (Tocilizumab; MRA). Other preferred humanized anti-IL-6 receptor antibodies include, for example, the antibodies described in WO2009/041621. In another preferred embodiment, anti-IL-6 receptor antibodies include those that recognize the same epitope recognized by a humanized PM-1 antibody (Tocilizumab; MRA).

Specifically, examples of anti-gp130 antibodies include, but are not particularly limited to, the antibodies AM64 (JP-A (Kokai) Hei 3-219894), 4B11, 2H4 (U.S. Pat. No. 5,571,513), and B-P8 (JP-A (Kokai) Hei 8-291199).

The IL-6 variants used in the present invention are substances with the activity of binding to an IL-6 receptor and which do not transmit IL-6 biological, activity. That is, the IL-6 variants compete with IL-6 to bind to IL-6 receptors, but fail to transmit IL-6 biological activity, and thus block IL-6-mediated signal transduction.

The IL-6 variants are produced by introducing mutation(s) by substituting amino acid residues in the amino acid sequence of IL-6. The origin of IL-6 used as the base of the IL-6 variants is not limited, but is preferably human IL-6, considering antigenicity and such.

More specifically, amino acid substitutions are performed by predicting the secondary structure of the IL-6 amino acid sequence using known molecular modeling programs (e.g., WHATIF; Vriend et al., J. Mol. Graphics (1990) 8, 52-56), and further assessing the influence of the substituted amino acid residue(s) on the whole molecule. After determining the appropriate amino acid residue to be substituted, commonly performed PGR methods are carried out using a nucleotide sequence encoding a human IL-6 gene as a template, and mutations are introduced to cause amino acids substitutions, and thus genes encoding IL-6 variants are obtained. If needed, this gene is inserted into an appropriate expression vector, and the IL-6 variant can be obtained by applying the aforementioned methods for expression, production, and purification of recombinant antibodies.

Specific examples of the IL-6 variants are those disclosed in Brakenhoff et al., J. Biol. Chem. (1994) 269, 86-93, Savino et al., EMBO J. (1994) 13, 1357-1367, WO 96/18648, and WO 96/17869.

The IL-6 receptor partial peptides are peptides that comprise part or all of the amino acid sequence of the region of the IL-6 receptor amino acid sequence that is involved in the binding between the IL-6 and IL-6 receptor. Such peptides usually comprise ten to 80, preferably 20 to 50, more preferably 20 to 40 amino acid residues.

The IL-6 receptor partial peptides can be produced according to generally known methods, for example, genetic engineering techniques or peptide synthesis methods, by specifying the region of the IL-6 receptor amino acid sequence that is involved in the binding between the IL-6 and IL-6 receptor, and using a portion or entirety of the amino acid sequence of the specified region.

When preparing an IL-6 receptor partial peptide using genetic engineering methods, a DNA sequence encoding the desired peptide is inserted into an expression vector, and then the peptide can be obtained by applying the aforementioned methods for expressing, producing, and purifying recombinant antibodies.

When producing an IL-6 receptor partial peptide by using peptide synthesis methods, generally used peptide synthesis methods, for example, solid phase synthesis methods or liquid phase synthesis methods, may be used.

Specifically, the peptides can be synthesized according to the method described in “Continuation of Development of Pharmaceuticals, Vol. 14, Peptide Synthesis (in Japanese) (ed. Haruaki Yajima, 1991, Hirokawa Shoten)”. As a solid phase synthesis method, for example, the following method can be employed: the amino acid corresponding to the C terminus of the peptide to be synthesized is bound to a support that is insoluble in organic solvents, then the peptide strand is elongated by alternately repeating (1) the reaction of condensing amino acids, whose α-amino groups and branch chain functional groups are protected with appropriate protecting groups, one at a time in a C- to N-terminal direction; and (2) the reaction of removing the protecting groups from the α-amino groups of the resin-bound amino acids or peptides. Solid phase peptide synthesis is broadly classified into the Boc method and the Fmoc method, depending on the type of protecting groups used.

After synthesizing a protein of interest as above, deprotection reactions are carried out, then the peptide strand is cleaved from its support. For the cleavage reaction of the peptide strand, hydrogen fluoride or trifluoromethane sulfonic acid is generally used for the Boc method, and TFA is generally used for the Fmoc method. In the Boc method, for example, the above-mentioned protected peptide resin is treated with hydrogen fluoride in the presence of anisole. Then, the peptide is recovered by removing the protecting groups and cleaving the peptide from its support. By freeze-drying the recovered peptide, a crude peptide can be obtained. In the Fmoc method, on the other hand, the deprotection reaction and the reaction to cleave the peptide strand from the support can be performed in TFA using a method similar to those described above, for example.

Obtained crude peptides can be separated and/or purified by applying HPLC. Elution may be performed under optimum conditions using a water-acetonitrile solvent system, which is generally used for protein purification. The fractions corresponding to the peaks of the obtained chromatographic profile are collected and freeze-dried. Thus, purified peptide fractions are identified by molecular weight analysis via mass spectrum analysis, amino acid composition analysis, amino acid sequence analysis, or such.

Herein, “gemcitabine or a salt thereof” refers to 2′-deoxy-2′,2′-difluorocytidine or a salt thereof, which has the function of inhibiting nucleic acid synthesis by inhibiting DNA elongation when incorporated into DNA chains. A particularly preferred salt of gemcitabine is gemcitabine hydrochloride (Gemzar (registered trademark)).

IL-6 inhibitors of the present invention and gemcitabine or a salt thereof can be used to enhance the antitumor T cell response in tumor-bearing organisms by selectively eliminating immature myeloid cells (ImC) aberrantly proliferating and having the immunosuppressive activity or by suppressing the immunosuppressive activity. The cancer type in the subject—the tumor-bearing organisms—is not particularly limited, and may be any cancer, including pancreatic cancer, stomach cancer, prostatic cancer, head and neck cancer, breast cancer, lung cancer, colon cancer, and ovarian cancer.

Herein, “enhancement of the antitumor T cell response” also means an increase in the number of CD8⁺ T cells, enhancement of their activity, and an increase in interferon γ production. Furthermore, since the “antitumor T cell response-enhancing” effect of the present invention results in an antitumor effect, the reduction in tumor tissue volume is also regarded as part of the effect of the present invention.

Herein, when an IL-6 inhibitor is “administered in combination with” gemcitabine or a salt thereof, these agents may be administered at the same time or in succession, or one may be administered after a certain period of time following administration of the other. When an anti-IL-6 inhibitor is administered in combination with gemcitabine or a salt thereof, the doses may be appropriately adjusted depending on the subject's weight, age, symptoms, and such.

The above-described administration method, administration interval, and dose can be appropriately selected so as to achieve a therapeutic effect that is equivalent to the effect of the present invention. For example, the administration method, administration interval, or dose that achieves an effect that is equivalent to the above-mentioned preferable example can be selected by measuring the blood level of an above-described agent. Administration methods, administration intervals, and doses that achieve a blood level comparable to that shown in examples described above are also included in the present invention.

The subjects to whom a composition or agent of the present invention is administered are mammals. Preferred mammals are humans.

The compositions or agents of the present invention can be administered in the form of pharmaceuticals, either systemically or locally via oral or parenteral routes. For example, intravenous injections such as drip infusions, intramuscular injections, intraperitoneal injections, subcutaneous injections, suppositories, enemas, or oral enteric tablets can be selected. Appropriate administration methods can be selected depending on a patient's age and symptoms. The effective dose per administration is selected from the range of 0.01 to 100 mg/kg body weight. Alternatively, the dose may be selected from the range of 1 to 1000 mg/patient, preferably from the range of 5 to 50 mg/patient. A preferred dose and administration method are as follows: for example, when an anti-IL-6 receptor antibody is used, the effective dose is an amount such that free antibody is present in the blood. Specifically, a dose of 0.5 to 40 mg/kg body weight/month (four weeks), preferably 1 to 20 mg/kg body weight/month is administered via intravenous injection such as drip infusion, subcutaneous injection or such, once to several times a month, for example, twice a week, once a week, once every two weeks, or once every four weeks. The administration schedule may be adjusted, for example, by extending the administration interval of twice a week or once a week to once every two weeks, once every three weeks, or once every four weeks, while monitoring the condition of the patient and changes in the blood test values.

Herein, when an IL-6 inhibitor is administered in combination with gemcitabine or a salt thereof the dose can be appropriately adjusted depending on the subject's weight, age, symptoms, and such. When the IL-6 inhibitor is, for example, an anti-IL-6R antibody, its close is, for example, 0.1 to 100 mg/kg/week or a dose that gives an equivalent blood concentration as the above dose does, preferably 1 to 50 mg/kg/week or a dose that gives an equivalent blood concentration, and more preferably 5 to 20 mg/kg/week or a dose that gives an equivalent blood concentration. Alternatively, when the immunosuppressive agent is, for example, gemcitabine hydrochloride, its dose is, for example, 10 to 10000 mg/m²/week or a dose that gives an equivalent blood concentration as the above dose does, preferably 100 to 5000 mg/m²/week or a dose that gives an equivalent blood concentration, and more preferably 500 to 1500 mg/m²/week or a dose that gives an equivalent blood concentration.

The compositions or agents of the present invention may contain pharmaceutically acceptable carriers such as preservatives and stabilizers. “Pharmaceutically acceptable carrier” refers to a material that can be administered in combination with the above agents. Such pharmaceutically acceptable materials include, for example, sterile water, physiological saline, stabilizers, excipients, buffers, preservatives, detergents, chelating agents (EDTA and such), and binders.

In the present invention, detergents include non-ionic detergents, and typical examples of such include sorbitan fatty acid esters such as sorbitan monocaprylate, sorbitan monolaurate, and sorbitan monopalmitate; glycerin fatty acid esters such as glycerin monocaprylate, glycerin monomyristate and glycerin monostearate; polyglycerin fatty acid esters such as decaglyceryl monostearate, decaglyceryl distearate, and decaglyceryl monolinoleate; polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan tristearate; polyoxyethylene sorbit fatty acid esters such as polyoxyethylene sorbit fetrastearafe and polyoxyethylene sorbit tetraoleate; polyoxyethylene glycerin fatty acid esters such as polyoxyethylene glyceryl monostearate; polyethylene glycol fatty acid esters such as polyethylene glycol distearate; polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether; polyoxyethylene polyoxypropylene alkyl ethers such as polyoxyethylene polyoxypropylene glycol, polyoxyethylene polyoxypropylene propyl ether, and polyoxyethylene polyoxypropylene cetyl ether; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonylphenyl ether; polyoxyethylene hardened castor oils such as polyoxyethylene castor oil and polyoxyethylene hardened castor oil (polyoxyethylene hydrogenated castor oil); polyoxyethylene beeswax derivatives such as polyoxyethylene sorbit beeswax; polyoxyethylene lanolin derivatives such as polyoxyethylene lanolin; and polyoxyethylene fatty acid amides and such with an HLB of six to 18, such as polyoxyethylene stearic acid amide.

Detergents also include anionic detergents, and typical examples of such include, for example, alkylsulfates having an alkyl group with ten to 18 carbon atoms, such as sodium cetylsulfate, sodium laurylsulfate, and sodium oleylsulfate; polyoxyethylene alkyl ether sulfates in which the alkyl group has ten to 18 carbon atoms and the average molar number of added ethylene oxide is 2 to 4, such as sodium polyoxyethylene lauryl sulfate; alkyl sulfosuccinate ester salts having an alkyl group with eight to 18 carbon, atoms, such as sodium lauryl sulfosuccinate ester; natural detergents, for example, lecithin; glycerophospholipids; sphingo-phospholipids such as sphingomyelin; and sucrose fatty acid esters in which the fatty acids have 12 to 18 carbon atoms.

One, two or more of the detergents described above can be combined and added to the compositions or agents of the present invention. Detergents that are preferably used in the preparations of the present invention include polyoxyethylene sorbitan fatty acid esters, such as polysorbates 20, 40, 60, and 80. Polysorbates 20 and 80 are particularly preferred. Polyoxyethylene polyoxypropylene glycols, such as poloxamer (Plutonic F-68® and such), are also preferred.

The amount of detergent added varies depending on the type of detergent used. When polysorbate 20 or 80 is used, the amount is in general in the range of 0.001 to 100 mg/ml, preferably in the range of 0.003 to 50 mg/ml, more preferably in the range of 0.005 to 2 mg/ml.

In the present invention, buffers include phosphate, citrate buffer, acetic acid, malic acid, tartaric acid, succinic acid, lactic acid, potassium phosphate, gluconic acid, capric acid, deoxycholic acid, salicylic acid, triethanolamine, fumaric acid, and other organic acids; and carbonic acid buffer, Tris buffer, histidine buffer, and imidazole buffer.

Liquid preparations may be formulated by dissolving the agents in aqueous buffers known in the field of liquid preparations. The buffer concentration is in general in the range of 1 to 500 mM, preferably in the range of 5 to 100 mM, more preferably in the range of 10 to 20 mM.

The compositions or agents of the present invention may also comprise other low-molecular-weight polypeptides; proteins such as serum albumin, gelatin, and immunoglobulin; amino acids; sugars and carbohydrates such as polysaccharides and monosaccharides, sugar alcohols, and such.

Herein, amino acids include basic amino acids, for example, arginine, lysine, histidine, and ornithine, and inorganic salts of these amino acids (preferably hydrochloride salts, and phosphate salts, namely phosphate amino acids). When free amino acids are used, the pH is adjusted to a preferred value by adding appropriate physiologically acceptable buffering substances, for example, inorganic acids, and in particular hydrochloric acid, phosphoric acid, sulfuric acid, acetic acid, and formic acid, and salts thereof. In this case, the use of phosphate is particularly beneficial because it gives quite stable freeze-dried products. Phosphate is particularly advantageous when preparations do not substantially contain organic acids, such as malic acid, tartaric acid, citric acid, succinic acid, and fumaric acid, or do not contain corresponding anions (malate ion, tartrate ion, citrate ion, succinate ion, fumarate ion, and such). Preferred amino acids are arginine, lysine, histidine, and ornithine. Acidic amino acids can also be used, for example, glutamic acid and aspartic acid, and salts thereof (preferably sodium salts); neutral amino acids, for example, isoleucine, leucine, glycine, serine, threonine, valine, methionine, cysteine, and alanine; and aromatic amino acids, for example, phenylalanine, tyrosine, tryptophan, and its derivative, N-acetyl tryptophan.

Herein, sugars and carbohydrates such as polysaccharides and monosaccharides include, for example, dextran, glucose, fructose, lactose, xylose, mannose, maltose, sucrose, trehalose, and raffinose.

Herein, sugar alcohols include, for example, mannitol, sorbitol, and inositol.

When the compositions or agents of the present invention are prepared as aqueous solutions for injection, the agents may be mixed with, for example, physiological saline, and/or isotonic solution containing glucose or other auxiliary agents (such as D-sorbitol, D-mannose, D-mannitol, and sodium chloride). The aqueous solutions may be used, in combination with appropriate solubilizing agents such, as alcohols (ethanol and such), polyalcohols (propylene glycol, PEG, and such), or non-ionic detergents (polysorbate 80 and HCO-50).

The compositions or agents may further comprise, if required, diluents, solubilizers, pH adjusters, soothing agents, sulfur-containing reducing agents, antioxidants, and such.

Herein, the sulfur-containing reducing agents include, for example, compounds comprising sulfhydryl groups, such as N-acetylcysteine, N-acetylhomocysteine, thioctic acid, thiodiglycol, thioethanolamine, thioglycerol, thiosorbitol, thioglycolic acid and salts thereof, sodium thiosulfate, glutathione, and thioalkanoic acids having one to seven carbon atoms.

Moreover, the antioxidants in the present invention include, for example, erythorbic acid, dibutylhydroxy toluene, butylhydroxy anisole, α-tocopherol, tocopherol acetate, L-ascorbic acid and salts thereof, L-ascorbic acid palmitate, L-ascorbic acid stearate, sodium hydrogen sulfite, sodium sulfite, triamyl gallate, propyl gallate, and chelating agents such as disodium ethylenediamine tetraacetate (EDTA), sodium pyrophosphate, and sodium metaphosphate.

If required, the compositions or agents may be encapsulated in microcapsules (microcapsules of hydroxymethylcellulose, gelatin, poly[methylmethacrylic acid] or such) or prepared as colloidal drug delivery systems (liposome, albumin microspheres, microemulsion, nano-particles, nano-capsules, and such) (see “Remington's Pharmaceutical Science 16^(th) edition”, Oslo Ed., 1980, and the like). Furthermore, methods for preparing compositions or agents as sustained-release compositions or agents are also known, and are applicable to the present invention (Langer et al., J. Biomed. Mater. Res. 1981, 15: 167-277: Lancer, Chem. Tech. 1982, 12: 98-105; U.S. Pat. No. 3,773,919: European Patent Application No. (EP) 58,481: Sidman et al., Biopolymers 1983, 22; 547-556; and EP 133,988).

Pharmaceutically acceptable carriers used are appropriately selected from those described above or combined depending on the type of dosage form, but are not limited thereto.

Herein, the “subject” to be administered with a composition or agent of the present invention includes organisms and body parts of the organisms to which a composition or agent of the present invention is administered. The organisms are not particularly limited and include animals (for example, humans, domestic animals, and wild animals).

The “body parts of an organism” are not particularly limited; however, they preferably include areas affected by a disease.

Herein, “administering” includes oral and parenteral administrations. Oral administration includes administering in the form of an oral preparation. Oral preparations can be selected from dosage forms such as granules, powders, tablets, capsules, solutions, emulsions, or suspensions.

Parenteral administration includes administering in the form of injections. Injections include subcutaneous injections, intramuscular injections, and intraperitoneal injections. Alternatively, the agents of the present invention may be administered locally to target areas of treatment. For example, the agents can also be administered by local injection during surgery or using catheters.

When practicing the methods of the present invention together with other agents (for example, other cancer cell therapeutic agents or cancer vaccines), the agents of the present invention can be administered as a part of a pharmaceutical composition. In an embodiment, an agent of the present invention and another agent may be administered substantially at the same time.

All prior art references cited herein are incorporated herein by reference.

EXAMPLES

The present invention will be explained in detail, with reference to the Examples, but it is not to be construed as being limited thereto. A variety of alterations and modifications can readily be achieved by those skilled in the art, and such alterations and modifications are also included in the present invention.

Example 1 Antitumor Effect of Gemcitabine Hydrochloride (GEM) (1)

Cell line of methylcholanthrene-induced squamous cancer CMC-1 (2×10⁶ cells) was intradermally inoculated to BALB/c mice, and from day 5 after inoculation, GEM (Gemzar: gemcitabine hydrochloride) was intraperitoneally administered at 120 mg/kg every week. The tumor growth was measured every two days to evaluate the antitumor effect of GEM. The result is shown in FIG. 1.

GEM was administered to the tumor-bearing mice 30 days after CMC-1 inoculation, and after 48 hours the absolute number of respective cell populations in the spleen were analyzed by flow cytometry. The result is shown in FIG. 2. Cyclophosphamide (CY) (60 mg/kg), fluoro-5-uracil (5-FU) (120 mg/kg), or GEM was intraperitoneally administered to tumor-bearing mice 30 days after CMC-1 inoculation. After 48 hours, CD8⁺ cells were isolated from the spleen, and the growth ability after 60 hours of stimulation with immobilized anti-CD3 antibody (2 μg/ml) was assessed by ³H incorporation test. The result is shown, in FIG. 3.

The results demonstrate that GEM eliminates immunosuppressive cells and has an excellent growth-enhancing effect for CD8⁺ T cells in tumor-bearing organisms. Such an effect was not observed with CY or 5-FU. GEM was also demonstrated to have a tumor growth-suppressive effect.

Example 2 Antitumor Effect of Gemcitabine Hydrochloride (GEM) (2)

CMC-1 (2×10⁶) was intradermally inoculated to BALB/c mice. From day 5 after inoculation, GEM (120 mg/kg) was intraperitoneally administered every week and anti-CD8 antibody (250 μg) was intravenously administered every three days. The tumor diameter was measured every two days. The result, is shown in FIG. 4.

LLC-OVA (2×10⁶) prepared by introducing the ovalbumin (OVA) gene into mouse lung cancer cell line LLC was intradermally inoculated to C57BL6 mice, and after five days GEM (120 mg/kg) was intraperitoneally administered. After nine days, the regional lymph nodes were collected and assessed by flow cytometry for the proportion of OVA-specific CD8⁺ cytotoxic T cells. The result is shown in FIG. 5.

The results demonstrate that GEM produces the antitumor effect by enhancing the activity of CD8⁺ T cells.

Example 3 Antitumor Effect of Anti-IL-6R Antibody (MR 16-1) (1)

Cell line of methylcholanthrene-induced fibrosarcoma CMC-G4 (2×10⁶) was intradermally inoculated into BALB/c mice, and after one and two weeks the serum IL-6 concentrations were determined by ELISA. The result is shown in FIG. 6. After intradermal inoculation of CMC-G4, the anti-IL-6R antibody (MR16-1; Tamura, T. et al., Proc. Natl. Acad. Sci. USA (1993) 90, 11924-11928) (250 μg) was intravenously administered every three days. After 28 days, the spleen cells were collected and incubated in the presence of an anti-CD3 antibody (2 μg/ml) or concanavalin A (Con A: 2.5 μg/ml). After 36 hours of incubation, the IFN-γ concentrations in the culture supernatants were determined by ELISA. The result is shown in FIG. 7. In addition, the tumor diameter was measured every two days to evaluate the tumor growth-suppressive effect. The result is shown in FIG. 8.

The results show that the anti-IL-6 receptor antibody has the effect of enhancing IFN-γ production in tumor-bearing organism. This finding demonstrates that, as with GEM, the anti-IL-6 receptor antibody has an excellent effect of enhancing the activation of immunocompetent cells. The antibody was also demonstrated to have a tumor growth-suppressive effect.

Example 4 Effect of Combination Therapy Using Anti-IL-6R Antibody (MR16-1) and GEM

CMC-G4 (2×10⁶ cells) was intradermally inoculated to BALB/c mice, and from day 6 alter inoculation GEM (120 mg/kg) was intraperitoneally administered every week and anti-IL-6 receptor antibody MR16-1 (200 μg) was intravenously administered every three days. The tumor diameter was measured every two days. The result is shown in FIG. 9.

The result demonstrates that the combined use of gemcitabine (GEM) and anti-IL-6 receptor antibody (MR16-1) produces a more excellent antitumor effect than when each was administered alone.

INDUSTRIAL APPLICABILITY

The present invention demonstrated that the administration of an IL-6 inhibitor and/or gemcitabine or a salt thereof produces an excellent antitumor T cell response-enhancing effect in tumor-bearing organisms. Furthermore, it was shown that the T cell response-enhancing effect produces an excellent antitumor effect. 

The invention claimed is:
 1. A method for enhancing an antitumor T cell response and suppressing tumor growth in a tumor-bearing organism in need thereof, which comprises administering an anti-interleukin 6 (IL-6) receptor antibody and gemcitabine or a salt thereof to a tumor-bearing organism, wherein antitumor T cell response is enhanced and tumor growth is suppressed in the tumor-bearing organism in need thereof, and wherein the tumor-bearing organism has a cancer selected from the group consisting of stomach cancer, prostate cancer, head and neck cancer, breast cancer, lung cancer, colon cancer, and ovarian cancer, wherein the anti-IL-6 receptor antibody is a MR16-1 antibody or a PM-1 antibody.
 2. The method of claim 1, wherein the MR16-1 antibody or the PM-1 antibody is a chimeric antibody, a humanized antibody, or a human antibody. 